Lesson 6: Weather and Climate Topic Revision
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Transcript of Lesson 6: Weather and Climate Topic Revision
Weather and Climate
A Revision of Topics
Mr. T. Tonna
Mr. T. Tonna
Index
Topic One: Depressions Topic Two: Anticyclones Topic Three: Tropical Storms
– Case Study: Hurricane Katrina, 2005 Topic Four: Micro-Climate of an Urban Area Topic Five: Climate of The Maltese Islands Class Quiz- Who Wants to be a Millionaire?
Mr. T. Tonna
Depressions
Depressions are low pressure systems that form in the mid-latitude region (30°-60 ° N/S) when warm air meets cold air.
When this occurs the warm air is forced above the colder air. It then cools and clouds form which produce rain.
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Warm Front Cold Front Occluded Front
The Beginning of the depression
The End of the Depression
When the warm and cold fronts join.
Mr. T. Tonna
Mr. T. Tonna
Anticyclones
Anticyclones are formed from an area of high pressure.
They tend to bring clear, settled weather. In an anticyclone, air descends and pressure
increases. This brings very light winds (which blow outwards from the centre in a clockwise motion), clear skies and dry conditions (because the air is descending and warming up, there are no clouds and no rain).
Mr. T. Tonna
Winter Anticyclones
Summer Anticyclones
Dry and bright with very little cloud.
Very little cloud
Sun low in the sky, so cold conditions.
Dry with light winds
Clear evening skies mean that nights can be very cold.
Sun high in the sky, so hot and sunny
Early morning frost and fog may last all day.
Cloudless skies at night allow heat to escape, so nights can be cool.
Extensive low cloud or fog may produce overcast or ‘gloomy’ conditions.
Risk of thunderstorms at end of ‘heat wave’ conditions
Early morning dew and mist.
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Tropical Storms
Tropical storms are areas of extremely low pressure, they produce violent weather with high winds, thick cloud and torrential rain.
There are three main criteria needed for a tropical storm to develop:
Warm Tropical Oceans (Temperature of 24°C or more) Late Summer early Autumn where sea temperature is
optimum. In Certain Latitudes: 5°-20° North and South.
Mr. T. Tonna
Hurricane Katrina (2005) Hurricane Katrina formed as Tropical Depression over the
south-eastern Bahamas on August 23, 2005. It grew into a Category 5 Hurricane.
New Orleans had: Winds over 175miles per hour (over 280km/h); An estimated 80 percent of New Orleans was under water, up to 20 feet deep in places; The centre eye had a low pressure of 920 mbar.
1 million people homes destroyed $81 billion in damages. Oil facilities were damaged and as a result petrol prices
rose in the UK and USA. Total Estimated Damages exceeded $150 billion in
Louisiana and Mississippi alone.
Mr. T. Tonna
Micro-Climate of an Urban Area
A Micro-climate is a local atmospheric zone where the climate differs from the surrounding area.
Human activity has a big influence on the climate of an urban area.
Climate in Urban Areas are affected by human factors such as pollution, the colour of buildings, people themselves and factories etc.
An urban heat island (UHI) is a metropolitan area that is significantly warmer than its surrounding rural areas due to human activities.
Mr. T. Tonna
Mr. T. Tonna
Mr. T. Tonna
Climate of the Maltese Islands
The climate is typically Mediterranean, with hot, dry summers, warm and sporadically wet autumns, and short, cool winters with adequate rainfall. Nearly three-fourths of the total annual rainfall of about 600 millimetres (24 inches) falls between October and March; June, July, and August are normally quite dry.
The Rainfall and Temperature are highest in July and lowest in December.
Malta is extremely windy with only 7.7 % days considered as calm. Most common wind is the north-westerly ‘il-Majjistral’ (19% of the days in a year).
Mr. T. Tonna
Mr. T. Tonna
Quiz Time